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By James L. Parks, David M. Kjos

"Designs, installation procedures and performance characteristics of martensitic cast steel concaves are reviewed. Longer wear life, fewer pieces to install and eliminating the need to scarf joints are the principal benefits of using martensitic steel to replace austenitic12% Mn (Hadfield's) steel, the traditional concave material for large gyratory crushers. Installation procedures that reduce the risk of breakage are described. Operating practices that affect concave performance are also discussed.IntroductionThe crushing machine considered to be the forerunner of the modem gyratory crusher was patented in 1878 by Charles M. Brown of the Gates Iron Works(1). The earliest gyratory crushers with receiving openings of 6 to 12 inches were fed by hand, and the crushing capacity of a mine was increased simply by installing more small crushers. The introduction of the steam shovel to open pit mining around the tum of the century provided an incentive for much larger primary crushers, and gyratory crushers with a 48 in. receiving opening were being built by 1910, followed not long afterward by machines with 54 in. and 60 in. openings to . Fortunately for the crusher maintenance people of that era, an austenitic 12% Mn steel with exceptional toughness was already available, having been discovered by Robert Abbot Hadfieldoi in 1882. Although small gyratory crushers working soft- to medium-hard rock reportedly used chilled cast iron (white iron) wear parts, these newer and much larger machines were fitted with ""Hadfield's manganese steel"" concaves and mantles to withstand the impact associated with handling large rocks .M E International first challenged the long-standing convention of using 12% Mn steel concaves in large gyratory crushers in the late 1960s when they supplied upper row concaves in martensitic cast steel for a 60-109 primary crusher at a taconite plant on the Iron Range. Since then, martensitic steels have been successfully substituted for 12010 Mn steel in concaves for more than seventy primary gyratory crushers processing iron, copper and precious metals ores, industrial minerals and crushed stone.This paper reviews materials, designs and performance characteristics of martensitic steel concaves in large gyratory crushers. The principal benefits include significantly longer wear life, fewer pieces to install and the elimination of scarfing. Obtaining the full measure of these benefits and minimizing the risk of breakage is strongly dependent on installation procedures, which are described in some detail. Operating practices that can affect performance are also discussed."

Jan 1, 1993

By Glenn S. Wyman

CHUQUICAMATA, located in northern Chile in the Province of Antofagasta, is on the western slope of the Andes at an elevation of 9500 ft. Because of its position on the eastern edge of the Atacama Desert, the climate is extremely arid with practically no precipitation, either rain or snow. All primary blasting in the open-pit mine at Chuquicamata is done by the churn drill, blasthole method. Since 1915, when the first tonnages of importance were removed from the open pit, there have been many changes in the blasting practice, but no clear-cut rules of method and procedure have been devised for application to the mine as a whole. One general fact stands out: both the ore and waste rock at Chuquicamata are difficult to break satisfactorily for the most efficient operation of power shovels. Numerous experiments have been made in an effort to improve the breakage and thereby increase the shovel efficiency. Holes of different diameter have been drilled, the length of toe and spacing of holes have been varied, and several types of explosives have been used. Early blasting was done by the tunnel method. The banks were high, generally 30 m, requiring the use of large charges of black powder, detonated by electric blasting caps. Large tonnages were broken at comparatively low cost, but the method left such a large proportion of oversize material for secondary blasting that satisfactory shovel operation was practically impossible. Railroad-type steam and electric shovels then in service proved unequal to the task of efficiently handling the large proportion of oversize material produced. The clean-up of high banks proved to be dangerous and expensive as large quantities of explosive were consumed in dressing these banks, and from time to time the shovels were damaged by rock slides. As early as 1923 the high benches were divided, and a standard height of 12 m was selected for the development of new benches. The recently acquired Bucyrus-Erie 550-B shovel, with its greater radius of operation compared to the Bucyrus-Erie 320-B formerly used for bench development, allowed the bench height to be increased to 16 m. Churn drill, blasthole shooting proved to be successful, and tunnel blasts were limited to certain locations where development existed or natural ground conditions made the method more attractive than the use of churn drill holes. Liquid oxygen explosive and black powder were used along with dynamite of various grades in blast-hole loading up to early 1937. Liquid oxygen and black powder were discontinued because they were more difficult to handle due to their sensitivity to fire or sparks in the extremely dry climate. At present ammonium nitrate dynamite is favored because of its superior handling qualities and its adaptability to the dry condition found in 90 pct of the mine. In wet holes, which are found only in the lowest bench of the pit and account for the remaining 10 pct of the ground to be broken, Nitramon in 8x24-in. cans, or ammonium nitrate dynamite packed in 8x24-in. paper cartridges, is being used. This latter explosive, which is protected by a special antiwetting agent that makes the cartridges resistant to water for about 24 hr, currently is considered the best available for the work and is preferred over Nitramon. Early churn drill hole shots detonated by electric blasting caps, one in each hole, gave trouble because of misfires caused by the improper balance of resistance in the electrical circuits. Primarily, it was of vital importance to effect an absolute balance of resistance in these circuits, the undertaking and completion of which invariably caused delays in the shooting schedule. Misfires resulting from the improper balance of electrical circuits, or from any other cause, were extremely hazardous, since holes had to be unloaded or fired by the insertion of another detonator. The advent of cordeau, later followed by primacord, corrected this particular difficulty and therefore reduced the possibility of missed holes. After much experimentation, the blasting practice evolved into single row, multihole shots, with the holes spaced 4.5 to 5 m center to center in a row 7.5 to 8 m back from the toe. Sucti shots were fired from either end by electric blasting caps attached to the main trunk lines of cordeau or primacord. The detonating speed of cordeau or primacord gave the practical effect of firing all holes instantaneously. Double row and multirow blasts, fired instantaneously with cordeau or primacord, proved to be unsatisfactory in the type of rock found at Chuquica-

Jan 1, 1953

By George W. Maynard

At the Pittsburg meeting of the Institute, May, 1879, I made the first announcement in America of the results obtained by Sidney Gilchrist Thomas and Percy C. Gilchrist, in their efforts to eliminate phosphorus in the manufacture of steel in the Bessemer converter and the open-hearth furnace.' The first published statement in an American newspaper was a reprint of the first Thomas-Gilchrist paper,which I sent to J. C. Bayles, at that time the editor. At the suggestion of many friends who were present at the Pittsburg meeting, and others who are cognizant of the beginnings of the process in the United States, and for the information of the younger generation of the iron and steel fraternity, I have thought it eminently proper that the history of the process in detail should be given where I made the first announcement and where the process has had its largest development. During my residence in England, from April, 1873, to February, 1879, and as a member of the Iron and Steel Institute since 1874, I was present at many of its meetings during those years. At nearly every meeting the burden of discussion was the question of the use of pig-iron containing phosphorus in the manufacture of steel by the Bessemer or the open-hearth process. In my biographical notice of Thomas: read at the New york meeting of the Institute, February, 1885, I show. that the working-out of the process was not a hap-hazard or accidental inspiration, but the culmination of many years of investigation of experiments and theories which had been carried on aid advanced by chemists and metallurgists at home and abroad.

Jan 1, 1911

By J. H. Swisher

When an Fe-Mn alloy is internally oxidized, the inclusions formed are MnO which contains some dissolzled FeO. In the internal oxidation reaction, not all of the manganese is oxidized; some remains in solid solution as a result of the high Mn-0 solubility product in iron. Taking these factors into consideration, the rate of internal oxidation of an Fe-1.0 pct Mn alloy is computed as a function of temperature, using available thermodynanzic data and recently published data for the solubility and diffusivity of oxygen in iron. The predicted and experimentally determined rates for the temperature range from 950 to 1350°C are in good agreement. ThE rates of internal oxidation of austenitic Fe-A1 and Fe-Si alloys have been studied extensively.1"4 Schenck et al. report the results of a few experiments with Fe-Mn alloys at 854" and 956C, and Bradford5 has studied the rate of internal oxidation of commercial alloys containing manganese in the temperature range from 677" to 899°C. When Fe-Mn alloys are internally oxidized, the inclusions formed are solutions of FeO in MnO, the composition depending on the experimental conditions. Since the thermodynamics of the Fe-Mn and FeO-MnO systems have been investigated,6"9 and since the solubility and diffusion coefficient of oxygen in y iron have been determined recently,' it is possible to predict the rate of internal oxidation from known data. The calculations used in predicting the rate of internal oxidation will first be outlined, then the results of the prediction will be compared with the experimental results of this investigation. PREDICTION OF PERMEABILITY FROM THERMODYNAMIC AND DIFFUSIVITY DATA Oxygen is provided for internal oxidation in these experiments by the dissociation of water vapor on the surface of the alloy. The dissociation reaction is: + H2(g) + [O] [1] where [0] denotes oxygen in solution. The equilibrium constant for this reaction is known as a function of temperature:' log As oxygen diffuses into the alloy, oxide inclusions are formed which are MnO with some FeO in solid solution. The reactions occurring are: [Mn] + [0] = (MnO) [31 and [Fe] + [0] = (FeO) [41 where [ Mn] is manganese dissolved in iron and (FeO) is iron oxide dissolved in MnO. The overall reactions may be written as follows: [Mn] + HOte) = (MnO) + H2(£) [5] and [Fe] + H20(g) = (FeO) + Hz(R) [61 The standard free-energy changes and equilibrium constants for Reactions [5] and [6] are known.6 Therefore the equilibrium constants for Reactions [3] and [4] may be obtained by combining known thermodynamic data for Reactions [I], [5], and [6]. For Reactions [3] and [4]: K = and For the present purpose, both the Fe-Mn7,8 and FeO-~n0' systems can be considered to be ideal, i.e., [amn] = [NM~] and (aFeO) = (NM~~) = 1 - (NFeO) where the Ns are mole fractions. These relations, together with Eqs. [I] and [8], permit us to compute both the oxide and metal compositions as a function of temperature and oxygen potential at any point in the specimen. For cases where the oxygen concentration gradient between the surface and the subscale-base metal interface is linear, the kinetics of internal oxidation is an application of Fick's first law: where dn/dt is the instantaneous flux of oxygen into the specimen, g-atom per sq cm sec; 6 is the instantaneous thickness of the subscale, cm; Do is the diffusion coefficient of oxygen in iron, sq cm per sec; p is density of iron, g per cu cm; h[%O] is the oxygen concentration difference between the surface and sub-scale-base metal interface, wt pct. B6hm and ~ahlweit" derived an exact solution to the diffusion equation for systems in which there is a stoichiometric oxide formed. They showed that the oxygen concentration gradient is given by a rather complex error function relation. For the Fe-Mn-0 system and for most other systems that have been studied, however, variations in oxide compositions are small and rates of internal oxidation are sufficiently slow that the deviation from linearity in the concentration gradient of oxygen is negligible. The mass of oxygen transported across a unit area of the specimen for the total time of the experiment is given by the mass balance equation:

Jan 1, 1969

By Charles Morris, Patricia Petty

Charles Morris Minerals engineers have a new opportunity to shape their industry's future. They can help secondary school teachers in their own communities improve their scientific knowledge and thus be better prepared to teach their students. Local sections of AIME and other groups are being asked to sponsor expense-aid scholarships for teachers who complete the summer field course A Total Concept of the Mining Industry. Now in its 18th year, the six-week summer course is presented by the Colorado Mining Association Education Foundation Inc., in cooperation with the Colorado School of Mines Office of Special Programs Continuing Education. The course will be held June 9 through July 18. "In the past, we have been successful in soliciting support for teacher-scholars from many organizations, corporations, and individuals within the industry," said John Robertson, Jr., Foundation chairman. "Now we hope to enlist the help of engineers at the grass roots level in identifying qualified local teachers and giving them what it takes to participate in this continuing education program." Robertson said the course provides secondary school teachers, counselors, and administrators with a working knowledge of the mining and metallurgical industries. It also helps teachers recognize career opportunities for their students. "With the industry facing a challenging new era, we must have teachers who can relate the excitement of this challenge to their students. They will inspire future generations of resource finders, developers, and managers," he said. More than 670 teachers in 27 states, including 45 graduates of the "class of '85" have completed the course and gained six semester hours of graduate credit. The Foundation's Planning and Curriculum Committee meets regularly to develop the course outline and recruit the faculty. Lecturers are selected on their ability to communicate with people not familiar with the industry. Last year, 67 faculty members came at their own time and expense to discuss their specialties, ranging from exploration to marketing. Normally, teachers receive scholarship aid in the form of tuition and fees, and transportation and meals while on field trips. Expense-aid scholarships cover room and board on campus for those beyond the Denver-Metro area, and travel to and from Golden. "We hope to broaden the appeal and the geographical range of the program," Robertson said. Inspiration for the field summer program for teachers came in 1967 from a mining engineer, the late C.L. (Lindy) Barker, a 1931 graduate of the Colorado School of Mines. Barker and a group of concerned individuals convinced the Colorado Mining Association to accept sponsorship of the course in 1968. The Colorado School of Mines and its Office of Special Programs and Continuing Education agreed to be a co-sponsor to give it accreditation and provide physical facilities and coordination. The first course was held in 1969. Operating funds were solicited from industry to pay tuition, course material, the cost of a course coordinator, field trips, and overhead. Through the years, personal contact by an industry representative has been the most effective teacher recruiting tool. Through expense-aid scholarships provided by local sections of professional organizations, such as AIME, as well as CSM alumni and other friends, there will now be a greater incentive for more teachers to get to know the minerals industry and pass that knowledge on in the classroom.

Jan 3, 1986

By Nobuaki Sato

For the recovery of uranium from spent nuclear fuel, sulfide reprocessing process, which consists of voloxidation, selective sulfurization, and magnetic separation or selective dissolution steps, are proposed. In this paper selective sulfurization of rare-earth oxides in the presence of uranium oxides was studied by thermogravimetry and X-ray diffractometry. In case of the mixture with UO2, the rare earth oxides R2O3 (R=Nd, Eu, etc.) were preferentially sulfurized by CS2 formingoxysulfides and sulfides, while UO2 remained at temperatures lower than 500 °C. When R2O3was mixed with U3O8, first, the reduction of U3O8 to UO2 occurred at low temperatures followed by the sulfurization of R2O3. The separation of rare earth elements from UO2 in suspensionsolution by the use of permanent magnet was examined. The advantage of the proposed process was also discussed by compared with current process.

Jan 1, 2006

NEW YORK LOCAL SECTION Executive Committee Louis D. HUNTOON, Chairman ARTHUR S. DWIGHT, Vice-Chairman THOMAS T. READ, Secretary, Woolworth Bldg., New York, N. Y. E. MALTBY SHIPP, Treasurer GEORGE F. KUNZ W. DE L. BENEDICT Meeting, Jan. 16, .1914 A meeting of the New York Local Section of the American Institute of Mining Engineers was held at the Engineering Societies Building, 29 West 39th Street, New York City, Jan 16 1914 the Chairman, -L. D. Huntoon, presiding. Forty members weld present. In the absence of the Secretary, C. A. Bohn was appointed Secretary pro teen. N. H. Darton, Geologist of the U. S. Geological Survey, delivered an address on. The Occurrence of Gas in Coal, illustrated by lantern slides of charts, curves, and tables showing various features of gas occurrences. J. W. Richards, J. T. Beard, W. L. Saunders, L. D. Huntoon, and Mr. Darton participated in the discussion which followed the address. THOMAS T. READ; Secretary.

Jan 3, 1914

By Thomas P. Oxford

The impact of recent legislation on Florida phosphate industry operations has been dramatic. The most significant influences are described: the National Environmental Policy Act of 1969; the Federal Water Pollution Control Act Amendments of 1972; and implementation of the Florida Environmental Land and Water Management Act of 1972. Further discussion includes: critical examination of the recently completed EPA Areawide EIS; potential effects of the Resource Conservation and Recovery Act of 1976; the Surface Mining Control and Reclamation Act of 1977; current local and state laws; and summary of studies on radiochemical effects of mining, seepage from gypsum ponds, and dewatering of waste clays.

Jan 1, 1979

By C. A. Fisher

THE advent of the Rocky Mountain States into prominence as an oil-producing region is comparatively recent. Scarcely more than a decade has passed since the number of producing oilfields in this part of the country were few and their combined yield small and relatively unimportant. However, oil was discovered and recorded near the present site of Lander, Wyo., as early as 1833 and in 1867, on the comple-tion of the Union Pacific R. R., the site of this oil discovery was located, among other things, as a natural resource of economic importance. In that year a well was drilled for oil, to a depth of 480 ft., near Evanston, Wyo., but later was abandoned. In 1883, the Lander district witnessed the successful completion of the first oil well in the state. In Colorado, oil was first produced from shallow open wells near Canon City and sold to prospectors in 1864; in 1887, the Florence oilfield was discovered and a commercial production developed. While the Rocky Mountain States have never gained the prominence as an oil-producing region attained by the Pacific Coast, Mid-Continent, or Gulf fields, a substantial and increasing production is being taken from the Rocky Mountain province. At the close of 1923, the oil industry in this region has 38 oil and 21 gas fields producing, or capable of producing, oil or gas in a commercial way with a combined annual yield of nearly 47,000,000 bbl. of oil, a daily refining capacity aggregating about 90,000 bbl., upwards of 17,000,000 bbl. of crude in storage, and an 8-in. pipeline, nearing completion, 600 miles long which will connect the most prolific oilfield of the Rocky Mountain States with a trunk pipeline between Mid-Continent and the east at Carrollton, Mo. Several of the larger standard and independent operating companies are now represented in this region and, in the last ten years, there has been developed at Casper one of the large refining centers of the west. Fig. 1 illustrates the rise in production of four of the larger fields, also in the total production of the state; in addition there is given the yield of the larger fields of Wyoming and Montana for 1923.

Jan 3, 1924

By E. K. Landis

IK connection with the interesting paper of Mr. Glenn on "Sampling Ores Without Use of Machinery " (page 156 of the present volume), I venture to offer the results of ten years' experience in the sampling of iron-ore by a method adopted when I first became

Jan 1, 1892

By Ángel Azañero Ortiz

Dada la abundancia de los minerales sulfurados polimétalicos, se realizó un estudio de su comportamiento frente a la flotación diferencial. En ese sentido, el presente texto define los conceptos teóricos de la flotación selectiva a través de un estudio mineralógico y químico de la muestra. Así, las pruebas de flotación bulk y la separación reportan buenos resultados. De otro lado, el mineral de cobre, plomo y zinc que se ha estudiado no presenta dificultad durante la flotación selectiva. La calidad y la eficiencia de separación de los concentrados pueden ser mejorados con mayor tiempo de flotación y más etapas de limpieza.

Sep 1, 2012

By C. S. Sivil

To modern civilization the platinum metals are of inestimable value. Their distinctive properties, both physical and chemical, render them indispensable in an age in which the processes of the laboratory are becoming an essential part of the daily life of the world. Generally, their function, though vital to particular processes, is not spectacular, and so remains unknown to all except the operators. EARLY METHODS OF MANUFACTURE The properties of platinum were recognized as of prime importance for scientific work at. a very early date, probably between 1750 and 1760. The difficulty of making articles from it seemed almost insurmountable, because no means of attaining the temperature necessary to melt it were known at that time. It is true that solid platinum could be obtained by fusing the metal with a more volatile metal such as arsenic, which was subsequently driven off by baking, but such a method, at its best, would give only a very brittle product, which was totally unsuitable for the purposes for which it was intended. Little, if any, progress could be made until it was discovered that platinum sponge, heated to white heat and hammered in an iron or clay mold, would metallize and retain the shape of the mold. This was a process that could not be wholly satisfactory but from it developed the method of pressing the sponge in a mold and forging it at white heat into wire or sheet. At present a somewhat similar process must be used for fabricating articles of tungsten, molybdenum and other metals of high fusing point, as with these metals we face today the same problems that the scientists of the eighteenth century encountered with platinum, but possibly the next significant advance in the metallurgy of these metals will be the devising of means to melt and cast them.

Jan 1, 1931

By S S. Kanchibotla, I Brunton

Most blast fragmentation models assume the rock mass properties, explosive properties and blast design variables to be constants and uniformly distributed within a blast. However, in reality all these input variables vary within a blast resulting in variation in the resulting fragmentation size distribution. A stochastic modelling approach is introduced in this paper to quantify this variation. This technique takes the input variables as statistical distributions rather than constants and through several thousand iterations, generates a statistical representation of the expected fragmentation resulting from a production blast. A case study of three production blasts from a large open pit mine are presented and the modelled fragmentation æenvelopeÆ shows good agreement with the fragmentation æenvelopeÆ estimated from Split image analysis. The various blast-related parameters influence different parts of the fragmentation distribution, eg rock strength and explosive velocity of detonation have most impact on the fines. The technique is used to identify the parameters that have the greatest influence on various size fractions. Such an analysis will be useful to direct resources to efficiently minimise the variation.

Jan 1, 2001

By Waldemar Lindgren

Fifteen years ago, in his presidential address before the Washington Academy of Sciences,' Alfred H. Brooks said: "Applied geology can only maintain its present high position by continuing the researches which advance the knowledge of basic principles. Future progress in applied geology depends on progress in pure geology. Early in 1927, Dr. David White, then chairman of the Division of Geology and Geography of the National Research Council, appointed a committee "On the Processes of Ore Deposition," which was the first recognition by the Council of this branch of applied geology. This committee will not be able to solve the many complex problems involved; it can only clear the way, survey the field, state the problems and encourage systematic research. This short paper aims to outline and to analyze the present status of this kind of geological research, to ascertain the quality of the work and to suggest lines that might profitably be followed. Increasing Demand for Geologists Economic geology, or the art of geology, could develop only after the principles of geology and mineralogy had been established. Before that time it was merely a collection of trade rules accompanied by more or less wild speculations. Thus we observe the beginnings of economic geology in the period 1770-1820. Soon afterwards, the State Surveys were established in this country, with the realization that the natural resources should be investigated and described. Geology was hardly yet equal to the task of scientific research in relationships and genesis, however, and there followed a period of discouragement and stagnation. In the meanwhile, pure geology had again registered progress, and, based on its principles and also on the rapid mining development in the Cordilleran region, the present phase of the study of ore deposits began to take form. Raphael Pumpelly, S. F. Emmons and G. F. Becker were among the pioneers in this movement. The United States Geological Survey was organized. Ore deposits were scientifically described and studied along lines of structure and mineralogy; theories of genesis were advanced, not always permanent but based on sound induction.

Jan 1, 1928

By A. G. Belova

With the federal climate change legislation in progress, there is a need for demonstration-stage technologies aimed at providing clean energy from coal. Our research aims to experimentally illustrate the feasibility of capturing CO2 on a novel sorbent system from a gaseous stream. The gas is then released resulting in a regenerated sorbent and a pressurized stream of pure CO2 to be used for storage. The proposed sorbent is a ceramic honey-comb structured monolith coated with CaO supported on a high-surface area alumina. CaO is a natural acceptor of CO2 and our design ensures the physical stability and chemical reactivity of CaO over a large number of CO2 capture/release cycles. Furthermore, the use of the monolith ensures a uniform flow through the reactor, minimizes pressure drop across the reactor, and maximizes the surface reactive area. In this paper, we will present the results from a flow-through laboratory-scale reactor that establishes the efficiency of the proposed system to capture CO2. Future applications of the reactor include integration within the new-generation coal gasification power plants, such as IGGC, as means of providing decarbonized electricity.

Jan 1, 2010

By B. Chalmers, S. Wojciechowski

THE structure of the equiaxed zone of several A1-Cu samples mechanically stirred during unidirectional solidification was examined. The stirring was produced by rotary oscillation of the mold about its vertical axis.' It was found that in Some samples the structure is not of the same type over the whole of the equiaxed zone; it consists of regions with two different etching responses. Fig. 1 shows this structure in a Al-1 wt pct ku sample. The lighter etching regions with a coarse structure form something like a network and the darker etching regions with a finer structure can be observed as the continuation of the coarse structure inside this network. The difference in size and shape of the dendrite branches (they are rounded in the coarser structure) is similar to that found by Williamson and Chalmers in ice crystals solidified in undercooled water: when the amount of undercooling was small, the ice crystals were more rounded and coarser than these solidified with a larger amount of undercooling.' It seems justified to conclude that the observed structure resulted from solidification under different thermal conditions: the coarser structure solidified first out of the "purer" liquid and with a smaller amount of undercooling and the finer was formed later out of solute-enriched liquid under conditions of much more rapid heat extraction. A considerable change in the heat flow conditions at the later stages of solidification can be easily understood by taking into account that the coarser crystals form a continuous network and the amount of trapped liquid is relatively small; hence the contribution of latent heat is much smaller in the later stages of solidification. The difference in structure and etching characteristic reflects a difference in composition between these two regions. It was found that the darker etching re- gions are harder (30.4 to 31.3 HV5) than the lighter etching ones (25 to 26 HV5). A similar type of structure was found in a A1-4 wt pct Cu sample grown by Czochralski method. Fig. 2 shows the structure in the lower part of a sample grown slowly and then decanted by a rapid removing of the sample from the melt. In a few places trapped liquid solidified in the same manner as in the sample shown in Fig. 1.

Jan 1, 1968

CONTENTS PAGE Simons, Theodore.-Basic Principles of Gravity Concentration-A Mathematical Study : :.. 1 Taggart, Arthur F. and Gaudin, A. M.-Surface Tension and Adsorption Phenomena in Flotation 11 Hersam, Ernest A.-Factors Controlling the Capacity of Rock Crushers 12 Shaw, S. F.-The Ore Deposits of Sierra Mojada, Coahuila, Mexico 12 Wilson, Philip D.-The British Columbia Batholith and Related Ore Deposits 26 Greensfelder, N. S.-Shot-firing by Electricity 27 Mitke, Chas. A.-Metal Mine Ventilation in the Southwest 28 Foley, F. B. and Howell, S. P.-Neumann Bands as Evidence of Action of Explosives upon Metals 30 Schwartz, H. A., Payne, H. R., Gorton, A. F., and Austin, M. M.-Conditions of Stable Equilibrium in Iron-carbon Alloys 30

Jan 12, 1922

By David C. Scott

Between 1990 and 1991, the Bureau of Mines studied the mineral resources of the Kaibab National Forest to appraise the resources present and to determine the types of deposits, and their location. The study included a comprehensive literature search and a limited amount of field investigation of minerals and mining activity in and near the Forest. Small amounts of copper with lesser amounts of gold and silver have been produced from limestone-hosted, strata-bound deposits in the North Kaibab and Tusayan Ranger Districts. In addition to these small metallic deposits, volcanic cinders, pumice, flagstone, and sand and gravel have been quarried in the Chalendar and Williams Ranger Districts. At least ten uranium-mineralized breccia pipes have been identified in the Tusayan Ranger District, One of these, the Canyon pipe, contains a high-grade uranium ore body with associated silver, copper, lead, vanadium, and zinc. The mine permit for the Canyon pipe has been approved and the mine shaft head frame erected.

Jan 1, 1992

By Thomas Watson

INTRODUCTION THE users of barite in the United States derive their supply partly from the domestic production and partly from the imports from foreign countries. According to the Mineral Resource division of the U. S. Geological Survey, the domestic production of barite in 1913 was 45,298 short tons, valued at $156,275, or $3.45 a ton, and the imports of crude barite were 35,840 short tons, valued at $61,409, or $1.71 a ton. These figures clearly show a decided advantage in cost of the foreign over the domestic barite to users in the United States. The difference in cost is the only advantage to the consumer of foreign barite, for there are large reserves of the mineral in the United States of good grade. The production of many of the operating mines is capable of decided increase, and it is believed that the operating mines together with the large reserves of undeveloped deposits of barite are entirely adequate to meet the demands of the users in the United States. Deposits of barite are known in California, Idaho, Nevada, and Alaska, but most of them are undeveloped because there is, apparently, no market for the .material in that region. The domestic production is derived from Missouri and the Appalachian States, the greater part being obtained from Missouri. Following the outbreak of war in Europe many users of foreign barite in the United States have been forced to seek their supplies at home. It seems opportune at this time, therefore, that a general review be given of the barite industry in the Appalachian States, one of the two areas from which the domestic supply of the mineral is derived, and that attention be directed to the undeveloped deposits in the region. Briefly, then, this paper reviews the barite industry in the Appalachian States, and describes the occurrence, preparation, and uses of the mineral.

Jan 2, 1915

By Immo H. Redeker

Introduction In October of 1961 Texas Gulf Sulphur Company contacted the Asheville Minerals Research Laboratory, of the North Carolina State University, and requested assistance in the development of a phosphate ore body in Beaufort County. The main: objectives of the work at Asheville were defined as follows. The Laboratory should try to determine on the basis of drill core samples, submitted by Texas Gulf Sulphur Company, the highest grade of phosphate concentrate that could be obtained with high recoveries from North Carolina ore, the thickness of the ore body that could be treated economically in one section, and the quantity of concentrate that could be obtained per acre. The results should be compared with data obtained from the treatment of Florida ores. It was important to use mineral preparation methods during the initial laboratory work that could be verified later by continuous pilot plant operation and could be scaled-up for a commercial plant. The writer was in charge of the project at the Asheville Minerals Research Laboratory and participated in the development of one of North Carolina's greatest mineral resources from the first drill core examination to the production of the first poundage and tonnage quantities of flotation concentrates. The Lee Creek phosphate mine and mill was put in operation in early 1966 and can produce three million tons of phosphate concentrate a year. Sulfuric- acid, and phosphoric acid plant, diamonium phosphate plant and triple super phosphate plants came on stream in 1967; at that time they were the world's largest. Now that a phosphate industry has been established in the State, it]

Jan 1, 1971